[SixOfSpades]

My own technique is to have at least one party member designated as a Tank, which is essentially your best Fighter hopped up on steriods. Since you're a Paladin, you should fit this role admirably. Give all your best equipment to your Tank, so he's got the best Armor Class, highest hitpoints, and lowest Saving Throws. Now that this guy is practically invincible, what you do with him is shove him into the enemy's face--and keep him there. The enemies tend to focus on whichever member of your party they see first (so try to keep your Tank in front at all times), and if they have ranged weapons like Bows, they will stop shooting at your Mages & Thieves as soon as your Tank gets within melee range of them.

Most parties do well with 1 or 2 Tanks, some parties will have as many as three. A few people have reported doing well with parties of 6 archer-type characters, but I wouldn't suggest you try this yet. Also, you don't really need a Mage yet. If you want one, go ahead and have one, but don't feel like you need to drag one around just because you heard they were valuable. In the earlier stages of the game, you might just be happier with another Fighter-type to help you pound bad guys.

What I think your main difficulty is: You're a low-level party. None of you has any real hitpoints yet, so if anything happens, you die. Just grit your teeth, gain some EXP, and get those Level Ups.